Process for preparing carboxyl-functional silanes and siloxanes

Abstract

The invention relates to a process for preparing silanes or siloxanes having carboxyl functionalities, wherein a hydrogen silane or hydrogen siloxane compound is reacted with a tertiary butyl ester having an olefinic double bond and the sil(ox) ane-bonded tertiary butyl ester group is subsequently converted into the corresponding carboxyl group with elimination of isobutene.

We claim: 
     
       1. A process for preparing a silane or siloxane having carboxyl functionality, comprising (a) reacting the corresponding hydrogen silane or hydrogen siloxane with a tertiary butyl ester having an olefinic double bond and then (b) converting the tertiary butyl ester group on the product formed in step (a) into the corresponding carboxyl group and isobutene, and removing said isobutene. 
     
     
       2. A process according to claim 1, wherein step (a) is carried out using a hydrogen siloxane compound of the general formula (A) ##STR6## where the radicals R 1  are identical or different and each is an alkyl radical having from 1 to 4 carbon atoms or a phenyl radical provided that at least 90% of the radicals R 1  are methyl radicals. each R 2  is an alkyl radical having from 1 to 4 carbon atoms, a phenyl radical, or a hydrogen radical, but with at least one radical R 2  being a hydrogen radical, and   a in each occurrence is 0 to 100 and b in each occurrence is 0 to 5.   
     
     
       3. A process according to claim 1, wherein step (a) is carried out using a hydrogen silane compound of the general formula (B) ##STR7## where R a , R b  and R c  in the molecule are identical or different and each is a C 1  to C 18  aliphatic, aromatic, alkyloxy, or aryloxy radical, or a halogen radical. 
     
     
       4. A process according to claim 1 wherein step (b) is carried out with one or more tert-butyl esters of the formula   H.sub.2 C═C(R.sup.3)--C(O)O-t-Bu     where R 3  is H or CH 3 , or     H.sub.2 C═C(R.sup.3)--R.sup.4 --C(O)O-t-Bu,     wherein R 3  is H or CH 3 , and R 4  is an unbranched, branched or cyclic alkylene radical having from 1 to 30 carbon atoms and wherein R 4  is optionally interrupted by O or substituted by functional groups.   
     
     
       5. A process according to claim 2 wherein step (b) is carried out with one or more tert-butyl esters of the formula   H.sub.2 C═C(R.sup.3)--C(O)O-t-Bu     where R 3  is H or CH 3 , or     H.sub.2 C═C(R.sup.3)--R.sup.4 --C(O)O-t-Bu,     wherein R 3  is H or CH 3 , and R 4  is an unbranched, branched or cyclic alkylene radical having from 1 to 30 carbon atoms and wherein R 4  is optionally interrupted by O or substituted by functional groups.   
     
     
       6. A process according to claim 3 wherein step (b) is carried out with one or more tert-butyl esters of the formula   H.sub.2 C═C(R.sup.3)--C(O)O-t-Bu     where R 3  is H or CH 3 , or     H.sub.2 C═C(R.sup.3)--R.sup.4 --C(O)O-t-Bu,     wherein R 3  is H or CH 3 , and R 4  is an unbranched, branched or cyclic alkylene radical having from 1 to 30 carbon atoms and wherein R 4  is optionally interrupted by O or substituted by functional groups.   
     
     
       7. A process according to claim 1 wherein in step (a) the starting compounds are reacted in equimolar amounts at a temperature of from 60° to 140° C. in the presence of a transition metal catalyst. 
     
     
       8. A process according to claim 2 wherein in step (a) the starting compounds are reacted in equimolar amounts at a temperature of from 60° to 140° C. in the presence of a transition metal catalyst. 
     
     
       9. A process according to claim 3 wherein in step (a) the starting compounds are reacted in equimolar amounts at a temperature of from 60° to 140° C. in the presence of a transition metal catalyst. 
     
     
       10. A process according to claim 4 wherein in step (a) the starting compounds are reacted in equimolar amounts at a temperature of from 60° to 140° C. in the presence of a transition metal catalyst. 
     
     
       11. A process according to claim 5 wherein in step (a) the starting compounds are reacted in equimolar amounts at a temperature of from 60° to 140° C. in the presence of a transition metal catalyst. 
     
     
       12. A process according to claim 6 wherein in step (a) the starting compounds are reacted in equimolar amounts at a temperature of from 60° to 140° C. in the presence of a transition metal catalyst.